In case to carry out maintenance processing to the components of a computer system, only a unit apparatus as a maintenance object must be separated from the system in order to prevent the stop of the function or the operation of the system. For example, by migrating the function of a server as the maintenance object to another server (e.g. the standby system server), the maintenance (for example, the update and repair of a file) of the server becomes possible without stopping a function.
In case of carrying out the maintenance of a unit, a method of separating the maintenance object from the system and a method of restoring the unit separated after the maintenance to the system are disclosed in JP 2007-304845 (Patent Literature 1), JP 2009-146106A (Patent Literature 2), JP 2006-285597A (Patent Literature 3), and JP 2008-118236A (Patent Literature 4).
Patent Literature 1 discloses a computer system which updates software on a standby system virtual hardware and after that, and reduces a service stopping time in the update of the software by taking over the processing of the operating system to the standby system.
Patent Literature 2 discloses a storage system which switches a physical port which is an addition destination of a virtual port to another physical port, updates a routing table of a switch unit based on identifier data of the physical port of the addition destination, and changes an access path to an identical storage unit. Thus, the change of an access path becomes possible without stopping a computer.
Patent Literature 3 discloses a storage system which sets an address to a storage which is added or exchanged based on address conversion data set in advance, to a switch.
Patent Literature 4 discloses a maintenance method which switches a reception destination of a packet for a virtual address to the software of a new version from the software of an old version by switching the address corresponding to the virtual address.